Mobile-social gaming network OpenFeint, which was recently acquired by Japan’s GREE in April, announced an initiative today to bring more Facebook and social game developers over to its platform. OpenFeint currently claims 90 million users and 6,000 games across iOS and Android devices.

“We see more free-to-play and social game developers making a move [to mobile], and we want them to have the same kind of access that they’ve had on the web platform,” Fassett tells us. “In some instances, you are seeing traditional social game titles getting a straight port, and you’re also seeing [games] being built from the ground up.”

While the latter approach seems to be more popular with big players like Zynga creating a standalone games with Facebook game branding instead of straight ports, the former is still an option for developers with decent gameplay experiences. Fassett explains the trick is adapting game mechanics that work on web social networks to ones that are proven on mobile.

For example, he described a soon-to-be-released role-playing game for the OpenFeint platform that comes from a social network. The RPG uses friend gates where players must invite a certain number of new users before reaching the next level. While effective for a platform like Facebook, this invite mechanism falls flat on iOS or Android because the player is probably inviting players that already play the game instead of brand-new non-gaming users.

To adapt the mechanic to mobile, Fassett says that the developer instead focused on reengaging the existing user base through a player-versus-player interaction that keeps players playing. “Consider it almost like a fight mechanic,” he says. “The character needs to fight friends instead of inviting more friends to overcome the challenge. On mobile, developers have to think a little bit deeper about what a player is going to do when they have to help out another player.”

Aside from these lessons in gameplay translation, OpenFeint also offers social game developers an accessible network of existing users. This will likely come as a relief to social game developers intimidated by the fragmented nature of the mobile platform user base.

“Distribution is probably the biggest challenge,” Fassett says of social game developers entering the mobile space for the first time. “For us, the next phase is building the kinds of hooks into that user base that social game developers are used to. We also want to [educate] the user base that we have in game mechanics, like helping out your neighbor. That’s what I’ve come on to try and push and that’s what we’ll be doing over the next several months.”

At present, it’s free for developers to integrate OpenFeint’s SDK into their games. A new product called OFX, however, will feature some sort of monetization around integration — but the details haven’t been worked out.

“Our value is in the user based that we’ve acquired,” Fassett says. “We’re committed to cross platform, and if you look at [Apple’s Games Center], we’re almost two times their size and in terms of feature parity, we’re really out ahead of them. Granting access to [our user base] is another area that we look at for monetization.”

The one area where OpenFeint is not ahead of the game is HTML5 integration options for developers bold enough to experiment with it. Fassett tells us that while it is on the radar, OpenFeint remains focused on evolving its core SDK in the direction of free-to-play native apps.